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By this time, the German situation was at its worst. The Russians have established bridgeheads across the Oder and are now at the Seelow Heights, dubbed as the "Gates of Berlin" because it was the last cohorent line of defence before Berlin itself. On March 20, 1945, Heinrich Himmler was replaced by Gotthard Heirici as commander of Army Group Vistula. He predicted that the Soviets would attack over the Oder and at the Seelow Heights. The Heights was therefore defended by the Ninth Army of Theodor Busse with 112,143 men, 587 tanks and 2,625 guns. He depleted the men at the other parts of the line and turned the Oder floodplain into a swamp by releasing water from a dam to strengthen the Heights. They also made three defensive lines filled with anti-tank guns and ditches, bunkers, and trenches spreading back to Berlin. The reserves were the 11th SS Panzergrenadierdivision Nordland and 23rd SS Panzergrenadierdivision Nederland designated to counter any breakthrough.
By this time, the Soviet was able to muster and field2.5 million men, 6,250 tanks, 7,500 aircraft, 41,600 artillery pieces and mortars, 3,255 truck-mounted Katyusha rocket launchers, and 95,383 motor vehicles for the Berlin Operation. It vastly outnumbered the Germans in men and equipment